From Halopedia, the Halo wiki
As a variant of the standard armor worn by the Orbital Drop Shock Troopers, the UA/PPE variant shares many similarities. This version of the battle armor is specifically designed to aid an ODST in CQB-type combat conditions. The standard left pauldron is replaced with a longer two-piece ballistic plate, which aids in protecting the trooper's upper body while in a firing stance, and also to reduce severe injury from plasma-based weaponry. The helmet is also issued with an optics device that aids the user in relaying images and video to teammates or command.
During the Battle of Mombasa in 2552, ODST Michael Crespo donned close quarters ODST armor outfitted with additional demolitions gear in what was expected to be a boarding action on the CAS-class assault carrier Solemn Penance.
Halo 3: ODST
List of appearances